U.S. mortgage rates have suddenly jumped from near-record lows and are adding thousands of dollars to the cost of buying a home.

The average rate on the 30-year fixed loan soared this week to 4.46 percent, according to a report Thursday from mortgage buyer Freddie Mac.

That's the highest average in two years and a full point more than a month ago.

Brokers say rising rates are starting to influence Long Island transactions. An old practice known as "buy down points," where buyers pay banks an upfront fee to lower their rates, has returned, said Maria Kafetzis, an associate broker at Douglas Elliman Real Estate in Plainview.

The surge in mortgage rates follows the Federal Reserve's signal that it could slow its bond purchases later this year. A pullback by the Fed would likely send long-term interest rates even higher.

In the short run, the spike in mortgage rates might cause more people to consider buying a home soon. Rates are still low by historical standards.

But eventually, more expensive home loans could price some people out of the housing market.

Mortgage rates are rising because they tend to track the yield on the 10-year Treasury note.

The rate on 30-year loans soared from 3.93 percent last week to 4.46 percent this week -- the biggest one-week jump in 26 years.

A buyer who locked in a 3.35 percent rate in early May on a $200,000 mortgage would pay $881 a month, according to Bankrate.com. The same mortgage at a 4.46 percent rate would run $1,008 a month.

The difference: $127 more a month, or $45,720 over the lifetime of the loan.